Does the type of protein matter?

While protein can be found in both plant and animal foods, other nutrients in these sources differ. However, both work equally well to maintain muscle mass, strength, and bone mineral density, according to a study of 2,986 men and women between the ages of 19 and 72 by Harvard University and other Boston-area researchers. The study, published in the American Journal of Clinical Nutrition, also found that higher intake of protein increases strength and lean muscle mass in arms and legs, and noted that vitamins, minerals, and acidity of the diet (animal-based foods are more acidic) affect how protein is utilized.